revise readme.md

Author: huxiaoman7

README.md

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 | 876        | [Middle of the   Linked List    ](https://leetcode.com/problems/middle-of-the-linked-list) | Easy   | python、java、c++ |
 
 
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+### 栈·题目
+#### 基础题型
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+#### 表达式计算
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+#### 迭代极值
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+#### 栈的应用
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 ## LeetCode 1~400顺序题解
 - [python版本](https://github.com/huxiaoman7/leetcodebook/tree/master/python) | 已更新1~60
 - [java版本](https://github.com/huxiaoman7/leetcodebook/tree/master/java)